Final answer:
The incorrect statement about polynomial regression models is that they are a type of linear regression, as polynomial regression can model nonlinear relationships despite being categorized under multiple linear regression due to its polynomial terms.
Step-by-step explanation:
The statement that is not true about a polynomial regression model is B) It is a type of linear regression. Polynomial regression is capable of capturing nonlinear relationships since it can be of different degrees (quadratic, cubic, etc.), as stated in option C. It can indeed lead to overfitting when using a high-degree polynomial, which is mentioned in option D. Polynomial regression is considered a form of multiple linear regression, but the model itself models a nonlinear relationship between the independent variable(s) and the dependent variable due to the polynomial terms.